Altered EGFR localization and degradation in human breast cancer cells with an amphiregulin/EGFR autocrine loop.
The epidermal growth factor receptor (EGFR) and its ligand amphiregulin (AR) have been shown to be co-over expressed in breast cancer. We have previously shown that an AR/EGFR autocrine loop is required for SUM149 human breast cancer cell proliferation, motility and invasion. We also demonstrated that AR can induce these altered phenotypes when expressed in the normal mammary epithelial cell line MCF10A, or by exposure of these cells to AR in the medium. In the present studies, we demonstrate that SUM149 cells and immortalized human mammary epithelial MCF10A cells that over express AR (MCF10A AR) or are cultured in the presence of exogenous AR, express higher levels of EGFR protein than MCF10A cells cultured in EGF. Pulse-chase analysis showed that EGFR protein remained stable in the presence of AR, yet was degraded in the presence of EGF. Consistent with this observation, tyrosine 1045 on the EGFR, the c-cbl binding site, exhibited less phosphorylation following stimulation with AR than following stimulation with EGF. Ubiquitination of the receptor was also dramatically less following stimulation with AR than following stimulation with EGF. Flow cytometry analysis showed that EGFR remained on the cell surface following stimulation with AR but was rapidly internalized following stimulation with EGF. Immunofluorescence and confocal microscopy confirmed the flow cytometry results. EGFR in MCF10A cells cultured in the presence of EGF exhibited a predominantly intracellular, punctate localization. In stark contrast, SUM149 cells and MCF10A cells growing in the presence of AR expressed EGFR predominantly on the membrane and at cell-cell junctions. We propose that AR alters EGFR internalization and degradation in a way that favors accumulation of EGFR at the cell surface and ultimately leads to changes in EGFR signaling.
Willmarth
Nicole E
NE
Department of Cancer Biology, Kimmel Cancer Institute, Thomas Jefferson University, Philadelphia, PA 19107, USA.
Baillo
Andrea
A
Dziubinski
Michele L
ML
Wilson
Kristy
K
Riese
David J
DJ
Ethier
Stephen P
SP
D066258:Amphiregulin; D019898:Autocrine Communication; D001665:Binding Sites; D001943:Breast Neoplasms / Q000378:metabolism*; D002478:Cells, Cultured; D066255:EGF Family of Proteins; D004815:Epidermal Growth Factor / Q000378:metabolism / Q000494:pharmacology; D066246:ErbB Receptors / Q000096:biosynthesis / Q000378:metabolism*; D006023:Glycoproteins / Q000494:pharmacology*; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology*; D010766:Phosphorylation; D014407:Tumor Cells, Cultured; D054875:Ubiquitination; D015854:Up-Regulation
C587848:AREG protein, human; D066258:Amphiregulin; D066255:EGF Family of Proteins; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D004815:Epidermal Growth Factor; D066246:ErbB Receptors